Not extinct, just hiding: search for giant tortoise begins

Emma Woollacott, 10th January 2012

A species of giant tortoise long thought to be extinct now appears to be alive and well.

A genetic analysis by Yale University researchers has shown that dozens of Chelonoidis elephantopus tortoises - believed extinct for 150 years - may still be living at a remote location in the Galápagos Islands.

The researchers say that the direct descendants of at least 38 purebred individuals are living on the volcanic slopes of the northern shore of Isabela Island — 200 miles from their original home of Floreana Island, where they were hunted to extinction by whalers.

Now, scientists just need to find them.

"This is not just an academic exercise," says Gisella Caccone, a senior research scientist in the Department of Ecology and Evolutionary Biology.

"If we can find these individuals, we can restore them to their island of origin. This is important as these animals are keystone species playing a crucial role in maintaining the ecological integrity of the island communities."

The Yale team visited Volcano Wolf on the northern tip of Isabela Island in 2008 and took blood samples from more than 1,600 tortoises. These were compared with a genetic database of living and extinct tortoise species.

And analysis showed the genetic signatures of C. elephantopus in 84 Volcano Wolf tortoises, meaning one of their parents was a purebred member of the missing species. In 30 cases breeding had taken place within the last 15 years.

Since tortoises can live for 100 years, there's a good chance that many purebreds are still alive.

"To our knowledge, this is the first report of the rediscovery of a species by way of tracking the genetic footprints left in the genomes of its hybrid offspring," says former Yale postdoctoral researcher Ryan Garrick, now assistant professor at the University of Mississipi.

Even if no purebreds can be found, there's a good chance that the species can be resurrected through the intensive breeding of hybrids.

As for how the tortoises got there, the researchers say they were unlikely to have managed it on their own. Ironically, the very people to blame for their being wiped out on Floreana Island were probably responsible.

The tortoises were likely transported as food from Floreana, but either thrown overboard by whalers or left on the shore at Isabela Island, they say.